The result of special counsel Robert Mueller’s investigation into Donald Trump and his 2016 campaign should be a warning for the future, according to Democratic presidential candidate Pete Buttigieg.

Mueller and his team for two years probed whether there was collusion between the Trump campaign and Russia–as well as any obstruction of justice. However, Mueller ended his probe Friday without seeking indictments of Trump or any of his immediate family involved in the campaign.

“The president is not being indicted at the moment and also has not been exonerated at the moment. From a political perspective, I think this is further evidence it would be a mistake for Democrats to think that the way for the Trump presidency to end is by way of investigation,” Buttigieg, the two-term mayor of South Bend, Ind., said during a segment on MSNBC. “That could, of course, happen. But we’ve got to be paying attention to the kinds of conditions that made it possible for somebody like him to get here in the first place.”

“I would argue with—a figure like this president should never have been able to come within cheating distance of the Oval Office,” Buttigieg added. “And I fear if we’re not paying attention to the causes that he’s a symptom of, then not only is it possible for him to succeed in 2020, but we could also find ourselves with another figure like him or even worse in the future.”